Rails 3.2.8 - Multiple database access within one single Rails App

Question

I'm building a webapp that has its own database called 'products_db'. But my app will have to call reviews which is located in the database 'reviews_db', which is a legacy db being used by another system that I can't do anything because client wants it that way.

So, luckily both db are located in the same SQL Server (MSSQL). I've already have te 'activerecord-sqlserver-adapter' working but I need to figure out a way to access 'reviews_db' from my webapp.

The reviews_db doesn't follow any Rails convention because its a legacy system.

So, my class Product:

class Product < ActiveRecord::Base
  attr_accessible :name, :description, :price

  has_many :reviews

end

And my class Review:

class Review < ActiveRecord::Base

 # THIS CLASS DOESN'T FOLLOW RAILS CONVENTION
 # HOW DO I SET AND MANAGE LEGACY PRIMARY KEY?
 # HOW DO I CONNECT THIS MODEL TO THE OTHER DATABASE?
 # HOW DO I CONNECT THIS MODEL TO THE RIGHT TABLE NAME?

 attr_accessible :rv_tbl_title, :rv_tbl_id, :rv_tbl_text, :rv_tbl_author, :rv_tbl_ref_prod

 has_one :Product, foreign_key: :rv_tbl_author

end

Is there a gem for it? What's the solution to use in the Review class questions?

n_i_c_k · Accepted Answer · 2012-08-17 21:30:58Z

I'm not sure if this first part is necessary or not, but in your database.yml file, make a new connection by adding something like this to the end:

review:
  adapter: sqlserver
  database: reviews_db
  .... put your other configuration info here

Then in your review model review.rb:

class Review < ActiveRecord::Base
  establish_connection :review
  self.table_name = "review_table"
  self.primary_key = "review_id"
end

Change the table name to the correct table, and the primary key to the correct column name.

Then create a new table/model for the sole purpose of having a local reference to a review. So you could call it ReviewReference

class ReviewReference < ActiveRecord::Base
  belongs_to :review
  has_one :product
end

And change your Product model to

class Product < ActiveRecord::Base
  has_many :reviews, class_name: "ReviewReference"
end

This should get you a long way toward your goal. You might have to end up doing a lot of

@reviews = Review.where("some_column = ?", some_value)

or

@reviews = Review.find_by_sql("Some SQL Here") if you're doing more complex queries.

Sorry my answer isn't more concrete, I've only done this once. Props to Chad Fowler's Rails Recipes book for the concept.

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